Workpieces having limiting surfaces as mentioned above can be produced with lathes as described in GB-PS 1.222.986 or on griding machines as described in HU-PS 167 643. In these solutions, the limiting surfaces being non-cylindrical ones are manufactured by rotating the workpiece around its own axis as well as the axis of the workpiece around a second axis which is eccentrical to that of the workpiece. The brake points of the broken line of the limiting surfaces i.e. the number of corners of the produced surface profil are determined by the ratio between the numbers of revolutions of the respective axes. Further to this, the feed motion of the working tool must also be brought into harmony with the rotation of the axes.
In the known methods, these taks are solved by a mechanical control mechanism. Therein, the parts of the mechanism, i.e. also the main spindle and the eccentric spindle of the known working machines in a constant mechanical forced coupling or interlocking with one another. Therefore, a fine adjustment or a fine correction in the pre-set values of the control can not be carried out. This disadvantage results in the smaller accuracy of the parts produces according to the known solutions. This will be made understandable also by the fact that the known control mechanism of the known solutions are built from a great number of gear wheels and other constructional parts having forced interconnections between one another. As it is well known, a connection between two gear wheels has a certain accuracy in transfering the angular displacement from one wheel to the other. If a more than one connection of such wheels are arranged in series one after the other, the errors of motion transfer of the interconnections will sum up to a considerable difference between the prescribed or set angle position and the real or actual angle position of the spindles of the working machine.
Nevertheless, the above mentioned mechanism is quite noisy, its efficiency of power transfer is low as well as its duration is short. The main spindle of the working machine can be driven only slowly since the mechanical control mechanism don't allow a higher rotational speed.
The above mentioned defficiencies are of higher importance when the up-to-date control systems such as the numerically controlled working machines are also taken into consideration. In the machine industry, it is a common thing to solve all control problems by electronical methods and devices. However, the known solutions for producing these surfaces with broken-line circumferences are not adapted for applying the known electronical procedures and devices.
A further shortcoming of the known solutions is in that they are not suitable for producing workpieces with outer or inner limiting surfaces with polygonal profils generated by spiral-formed generatrix. The surfaces of the workpieces produced by the previous solutions can have only straight-lined generatrix.